There is a wide variety of systems used to trigger alarms under a multitude of circumstances. For example, car alarms sense vibration, house alarms sense motion and smoke alarms sense smoke. Often, alarms comprise at leas two units in communication with one another wherein one of the units generates some sort of alarm signal, be it by the detecting unit itself or by a remote unit separate from the detecting unit.
Other types of alarm systems include those which monitor the location of a person or article. Typically a first unit is a fixed unit. A second unit is typically a portable unit which is attached to a person or an article.
However, the systems of the prior art described herein do not provide for an alarm under the circumstances where, a traveling person who puts down his or her bag, looks up a moment too late to witness a thief making off with the bag. The traveling person, in this situation, has no way of calling attention to the thief as the theft is taking place nor knowing which direction the thief has gone in flight. Furthermore, the systems of the prior art do not speech synthesis means for announcing to the thief that the theft has been detected or other persons that the person carrying the stolen article is a thief.
The prior art includes a system, disclosed in U.S. Pat. No. 4,675,656 issued to Narcisse, which has a fixed first unit and a portable second unit, each transmitting and receiving signals. The portable second unit may include an alarm which may be triggered when the transmitter of the portable second unit sends a signal to the fixed first unit that a threshold condition has been reached.
Disclosed by Lemelson, issued U.S. Pat. No. 4,560,978, is a system including a fixed first unit and a portable second unit. The fixed first unit processes an alarm in the event that a threshold condition is reached by the portable second unit. This system also includes means for synthesizing speech at the second portable unit by receiving short wave transmissions generated at the fixed first unit. Such speech synthesis is not genera ed at the portable second unit.
Systems of the prior art may include least two portable units. For example, U.S. Pat. No. 4,598,272 issued to Cox, discloses two portable units, each transmitting and receiving signals. The system includes means for producing an audible alarm in the region of the second portable unit, such being activated at the first portable unit.
Furthermore, a system disclosed by Ayers, issued U.S. Pat. No. 4924,206, has, a first unit wired to an automobile and a portable second unit. The second unit transmits a signal to the first unit, and the first unit sends a signal to the second unit which is triggered by the absence of the second unit's transmitted signal. Each unit includes an alarm.
Each of the systems of the prior art described above provides for a monitor of a person's or article's distance from the first unit by electronic means. The goal achieved by the configurations of the prior art is that the first unit processes an alarm in the event that a threshold condition has been reached by the second unit.
The systems of the prior art described above do not provide for an alarm system having at least two portable units wherein the second portable unit activates and generates an alarm for indicating that the threshold condition has been reached. Moreover, the systems described above do not provide for the alarm of the second unit to include speech synthesizing means.